Abstract
The densification behavior, microstructure and mechanical properties of bulk TiB2-based ceramic composites, fabricated using the spark plasma sintering (SPS) technique with elements of (Fe–Ni–Ti–Al) sinter-aid were investigated. Comparing the change of shrinkage displacement of pure TiB2 and TiB2–5 wt% (Fe–Ni–Ti–Al), the addition of elements Fe–Ni–Ti–Al into TiB2 can facilitate sintering of the TiB2 ceramics. As the sintering temperature exceeds 1300 °C, the relative density does not significantly change. Alumina particles and austenite (Fe–Ni–Ti) metallic binder distributed homogeneously in the grain boundary of TiB2 can inhibit the growth of the TiB2 grains when the sintering temperature is below 1300 °C. The density and particle size of TiB2 greatly influence the mechanical behavior of TiB2–5 wt% (Fe–Ni–Ti–Al) composites. The specimen sintered at 1300 has the highest microhardness of 21.1 ± 0.1 GPa with an elastic modulus of 461.4 GPa. The content of secondary borides (M2B, being M = Fe, Ni), which are more brittle than TiB2 particles, can also influence the fracture toughness. The specimen sintered at 1500 °C has the highest fracture toughness of 6.16 ± 0.30 MPa·m1/2 with the smallest M2B phase. The results obtained provide insight into fabrication of ceramic composites with improved mechanical property.
Highlights
Titanium diboride (TiB2) has huge potential for applications such as ultra-high-temperature structural materials, cutting tools and lightweight armor materials because of a combination of attractive properties including high melting point, elastic modulus, chemical stability and hardness [1,2]
In the process of sintering, the densification behavior of a sample can be reflected by the displacement of the lower punch, which is automatically stored by the recording system
For the pure TiB2 powders, the densification process begins at approximately 1480 °C and ends at approximately 1790 °C, with approximately unimodal shrinkage rates
Summary
Titanium diboride (TiB2) has huge potential for applications such as ultra-high-temperature structural materials, cutting tools and lightweight armor materials because of a combination of attractive properties including high melting point, elastic modulus, chemical stability and hardness [1,2]. The inherent poor sinterability, brittleness and exaggerated grain growth at high temperature restrict the widely use of monolithic TiB2 ceramics in engineering applications [3,4]. Research results show that mechanical properties of TiB2 ceramics fabricated by the spark plasma sintering (SPS) process with Ti sinter-aid have significantly been improved [6]. Metallic elements, such as iron and nickel, which have lower melting point and better wettability, can be selected as additives for liquid phase sintering of TiB2 [7]. Exploring the use of combination between different metallic elements as sintering aid to enhance TiB2 ceramics becomes a necessary scientific question. Because of the plastic behavior of different metallic binder phases during fracture, the fracture toughness of the TiB2 composites is expected to be increased
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